NOTES: TSI is updated monthly with the index
numbers for the latest four months considered to be preliminary. With the
release of the preliminary number for the latest month, BTS also replaces the
number for the oldest preliminary month with a revised number.

SOURCE: U.S. Department of Transportation, Research
and Innovative Technology Administration, Bureau of Transportation
Statistics, Transportation Services Index, available at http://www.bts.gov/
as of February 2011.